Nutrient contamination, specifically regarding nitrogen and phosphorous, is widely recognized as an environmental concern. A significant and currently unregulated portion of nutrient pollution is produced from agricultural non-point sources. Previous studies have identified possible methods for treating nutrients from agricultural runoff; however, few studies have produced a treatment system capable of removing both nitrogen and phosphorous. Additionally, several previous studies utilized treatment methods which were expensive or difficult to maintain. The purpose of this study was to research several laboratory scale treatment systems in an effort to identify sustainable methods for treating nitrogen and phosphorous from synthetic agricultural runoff.
Three laboratory scale treatment configurations were developed and examined to determine the effectiveness of biological treatment methods. Configuration #1 consisted of an anaerobic denitrification biofilter with wood chip media. Configuration #2 included an anaerobic denitrification biofilter with corn residue media. Finally,
Configuration #3 consisted of an aerobic nitrification trickling filter with shredded tire media as well as an anaerobic denitrification biofilter with wood chip media. Synthetic agricultural runoff was conveyed through each configuration for four weeks, and samples were collected to measure the influent and effluent nutrient concentrations. Assessments of the sample data included advanced statistical analyses.
Additionally, a laboratory scale adsorption experiment was conducted to determine how effectively physical treatment methods reduce phosphorous contamination. Using crushed gypsum as the test substance, a series of adsorption isotherms were conducted by combining various masses of gypsum with test solutions of various phosphate concentrations. Samples were taken from each of these combinations to measure the adsorption of total phosphorous and reactive phosphorous over time. Data was analyzed in an effort to develop adsorption isotherm coefficients, and a supplemental crushed gypsum filter was then added to Configuration #1.
Results of the data analysis revealed that denitrification biofilters can substantially reduce total nitrogen contamination (20% reduction for the wood chip media denitrification biofilter in Configuration #1 and 34% reduction for the corn residue media denitrification biofilter in Configuration #2). Furthermore, the combination of a nitrification trickling filter with a denitrification biofilter can significantly improve the overall treatment of total nitrogen; Configuration #3 produced a 55% reduction in total nitrogen. Analysis of the adsorption tests revealed that gypsum was a suitable substrate for adsorbing phosphate. Adsorption rates as high a 41% and adsorption capacities as high as 1.4 milligrams of phosphate per each gram of gypsum were recorded.